The U.S. Soccer Federation confirmed Wednesday evening that defenders Fabian Johnson and Edgar Castillo will miss Friday’s World Cup qualifier in Antigua.

Johnson, who is ill, is expected to play in the Oct. 16 game against Guatemala. Castillo, who aggravated an injured foot, is out for both matches. Both Johnson and Castillo play primarily on the left.

Coach Jurgen Klinsmann’s roster, originally at 24 players, now has been reduced to 20. Midfielders Landon Donovan (knee) and Brek Shea (abdominal strain) were sent home Monday from the team’s Miami camp. Klinsmann has players available on standby but no call-ups were announced as of Wednesday night, and there were reports that no reinforcements would be called in for Friday’s game. Adjustments ahead of next week’s match in Kansas City are more likely.

The upcoming qualifiers are critical for the U.S. At 2-1-1, the Americans are level with Guatemala and Jamaica atop their four-team group. The first- and second-place teams following the Oct. 16 matches will advance to the final round of CONCACAF qualifying next year.

“Obviously, it’s a difficult situation losing Fabian for the Antigua game and Edgar being unavailable for both,” Klinsmann said. “We were in a similar situation for the first match against Antigua and Barbuda in June, and we will be prepared.”

Jose Torres, normally a midfielder, started at left back in that 3-1 win over Antigua in Tampa. He was not called into camp this time.

“Fabian has been ill since the weekend, and we were waiting to see if he would be healthy enough to join us in Miami,” Klinsmann said. “At this point, it is in everyone’s best interest to allow him to fully recover from his illness and come into Kansas City ready to play against Guatemala.

The U.S. now lacks a clear choice at left back. Captain Carlos Bocanegra, who typically plays in the middle, has significant experience on the left flank and could slide over. Michael Parkhurst recently has played out wide with Nordsjælland, his Danish club.

Klinsmann’s selection headache extends into midfield as well. The absence of Donovan and Shea will impact the team’s width, leaving the coach to rely on the likes of Graham Zusi or Sacha Kljestan, who are comfortable on the flanks but aren’t prototypical wingers.

Clint Dempsey, who played out wide during the 2010 World Cup, prefers to play further forward but might be an option under the circumstances. Klinsmann also has used Danny Williams on the flank, but the TSG Hoffenheim midfielder is far more effective centrally.